This invention relates to an ink supply device for an ink jet printer, and more particularly an ink supply device which keeps the viscosity of ink constant by the utilization of a constant flow rate pump, thus enabling a highly reliable printing operation.
In the charge amplitude control type of ink jet printers, variations in physical properties of ink greatly influence stability of the machines and in some cases disable the machines from effecting the printing operation.
As is well know, the viscosity of ink is time and temperature dependent. In a prior art ink jet printer having a constant pressure pump in an ink supply device, variations in the viscosity of ink cause variations in the size of printed characters, and brings the printing operation into disordered condition due to the accompanying nonuniform formation of ink drops over the progress of the printing operation. In other words, since variations in the viscosity cause variations in fluid resistance, they also lead to variations in the ejection rate of an ink beam from a nozzle, the period of time where the ink beam is flying in a deflection electric field, the amplitude of longitudinal deflection and eventually in the size of printed characters. The operation of forming the ink drops is further disturbed to an extent to disable the overall printer system.